Air Pollution Linked to Development and Progression of Chronic Lung Disease

Air pollution may adversely affect lung health by promoting the progression of lungs from a state of health to subsequently having chronic lung disease, chronic lung multimorbidity, and, ultimately, a fatal lung condition, according to study findings published in Thorax.

Limited evidence is available regarding the role played by air pollution in the progression of healthy lungs coming to have chronic lung disease, chronic lung multimorbidity, and subsequent death. The researchers sought to examine the associations of air pollution with different phases of chronic lung multimorbidity progression. They used data from the UK Biobank, a large-scale prospective study of UK adults.

A total of 265,506 participants were followed up from recruitment until the occurrence of 1 of the following 3 events: (1) all-cause death, (2) loss to follow-up, or (3) the end date of the follow-up (ie, October 31, 2015, in Scotland; July 31, 2019, in England and Wales). Outcomes of interest included asthma, chronic obstructive pulmonary disease (COPD), lung cancer, and death. Chronic lung multimorbidity was defined as the coexistence of at least 2 chronic lung diseases, including asthma, COPD, and/or lung cancer.

The annual concentrations of air pollutants, including particulate matter (PM)₁₀, PM_2.5, PM_2.5-10, nitrogen oxides (NO_x), and nitrogen dioxide (NO₂) were estimated with land-use regression models. Multistate models were utilized to evaluate the impact of air pollution on progression of chronic lung multimorbidity.

Over a median follow-up of 11.9 years, a total of 13,863 participants developed
at least 1 chronic lung disease, 1055 developed chronic lung multimorbidity, and 12,772 died. Differential associations of air pollution were observed with different trajectories of chronic lung multimorbidity.

Fine PM demonstrated the strongest associations with all lung health transitions, with hazard ratios (HRs) per 5 μg/m³ increase of 1.31 (95% CI, 1.22 to 1.42) and 1.27 (95% CI, 1.01 to 1.57) for transitions from healthy to incident chronic lung disease and from incident chronic lung disease to chronic lung multimorbidity, respectively; and HRs per 5 μg/m³ increase of 1.32 (95% CI, 1.21 to 1.45), 1.24 (95% CI, 1.01 to 1.53), and 1.91 (95% CI, 1.14 to 3.20) for mortality risk from healthy, incident chronic lung disease, and chronic lung multimorbidity, respectively.

Among the 5 air pollutants included in the analysis, PM with an aerodynamic diameter of 2.5 μM or less exhibited the greatest associations with the progression trajectory of chronic lung multimorbidity.

Several limitations of the current analysis warrant mention. To begin, exposure to air pollution in this study was evaluated according to the residential address reported at baseline, which might lead to exposure misclassification. Additionally, potential changes in time-varying factors at the time of transition could not be accounted for in this analysis. Further, because of the small proportion of follow-up data available on relevant confounders, the researchers used only the information provided at baseline in their study.

“From a clinical perspective, our findings have indicated the serious health concerns [that] arise due to high-level air pollution following incident chronic lung disease,” the authors noted. “From a public health perspective, efforts to reduce ambient air pollution can have positive impacts on ameliorating the health burden of respiratory multimorbidity,” they concluded.